Acronyms:
3GPP3rd generation partnership projectANaccess node (such as base station, node B, or e-Node B)D2Ddevice-to-deviceDRSFD2D registration server functionE-UTRANevolved UTRANFSUflexible spectrum useHOhandoverLTElong term evolution (of UTRAN/E-UTRAN)NWnetwork (RAN)RANradio access networkRATradio access technologyRRCradio resource controlUEuser equipmentUTRANuniversal terrestrial radio access networkWLANwireless local area network
This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
D2D communications, alternatively termed mobile-to-mobile (M2M), machine-to-machine (M2M), terminal-to-terminal (T2T) or peer-to-peer (P2P) communications, concerns wireless communications directly between UEs and is targeted for standardization sometime beyond 3GPP LTE Release 10 (also referred to as LTE-Advanced or LTE-A). D2D communications differ from cognitive radio in that in D2D the UEs communicate over radio resources allocated by the host cellular system/base station while in cognitive radio the UEs opportunistically use spectrum ‘holes’ that happen to go unused by the cellular system. In D2D the cellular network assures interference is controlled by its allocation of radio resources, whereas in cognitive radio the UEs are responsible for avoiding the primary users such as the D2D users and more traditional cellular users. The D2D communications therefore use licensed radio spectrum under supervision and control of the supporting cellular systems, and in fact may use the same radio resources as the supporting cellular systems.
There are several advantages in cellular operators supporting D2D communications, such as: reducing transmitter power consumption; improving spectrum efficiency and network resource utilization; increasing cellular network capacity and coverage; and creating support for additional services such as for example using the D2D devices as relays to form a co-operative mesh-type relay network.
A problem arises in that the D2D devices which desire to communicate directly may be attached to cells of different network operators. Network operators may realize much of the above advantages without supporting inter-RAN D2D, and it is expected that inter-RAN D2D will prove burdensome on network operators. The regular resource allocation, monitor and control mechanisms in current cellular networks are not designed for localized and distributed D2D communications in which user data transmission as well as control signaling (at least in part) happen directly between two or more UEs. Furthermore, the UE is not a trusted entity from the network operators' perspective, and so allowing UEs too much autonomy in directing D2D communications may create a threat of unauthorized usage of radio resources which the operators control.
Two references are relevant. In an article entitled MULTI-OPERATOR COGNITIVE RADIOS SHARING ONE CHANNEL by Anwer Al-Dulaimi and Hamed Al-Raweshidy (MobiWAC '09, Tenerife, Canary Islands, Spain, Oct. 26-27, 2009; published in Proceedings of the 7th ACM international Symposium on Mobility Management and Wireless Access, pp. 114-117), the concept of coordinated spectrum sharing among operators/service providers for the secondary usage of the radio resources is explored in which all primary and secondary operators should be connected to the common spectrum broker and any peer user using a channel must get the spectrum broker's agreement. But this reference is not seen to address how to setup a direct communication between peer users from different operators. US Patent Application Publication 2009/0221325 briefly mentions that D2D communication could take place among devices belonging to different operators but is not seen to provide any details as to how such communications might be established.
What is needed in the art is a way to facilitate D2D or other such direct communications between devices/UEs that are operating in different cells under the control of different RAN operators.